Re: [PATCH 2/2] cpufreq: qcom-hw: Add support for QCOM cpufreq HW driver

[Taniya Das <tdas@codeaurora.org>]

Hello Stephen,

On 10/18/2018 5:02 AM, Stephen Boyd wrote:
> Quoting Taniya Das (2018-10-11 04:36:01)
>> --- a/drivers/cpufreq/Kconfig.arm
>> +++ b/drivers/cpufreq/Kconfig.arm
>> @@ -121,6 +121,17 @@ config ARM_QCOM_CPUFREQ_KRYO
>>
>>            If in doubt, say N.
>>
>> +config ARM_QCOM_CPUFREQ_HW
>> +       bool "QCOM CPUFreq HW driver"
> 
> Is there any reason this can't be a module?
> 

We do not have any use cases where we need to support it as module.

>> +       depends on ARCH_QCOM || COMPILE_TEST
>> +       help
>> +         Support for the CPUFreq HW driver.
>> +         Some QCOM chipsets have a HW engine to offload the steps
>> +         necessary for changing the frequency of the CPUs. Firmware loaded
>> +         in this engine exposes a programming interface to the OS.
>> +         The driver implements the cpufreq interface for this HW engine.
>> +         Say Y if you want to support CPUFreq HW.
>> +
>>   config ARM_S3C_CPUFREQ
>>          bool
>>          help
>> diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
>> new file mode 100644
>> index 0000000..fe1c264
>> --- /dev/null
>> +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
>> @@ -0,0 +1,354 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (c) 2018, The Linux Foundation. All rights reserved.
>> + */
>> +
>> +#include <linux/cpufreq.h>
>> +#include <linux/init.h>
>> +#include <linux/kernel.h>
>> +#include <linux/of_address.h>
>> +#include <linux/of_platform.h>
>> +
>> +#define LUT_MAX_ENTRIES                        40U
>> +#define CORE_COUNT_VAL(val)            (((val) & (GENMASK(18, 16))) >> 16)
>> +#define LUT_ROW_SIZE                   32
>> +#define CLK_HW_DIV                     2
>> +
>> +enum {
>> +       REG_ENABLE,
>> +       REG_LUT_TABLE,
>> +       REG_PERF_STATE,
>> +
>> +       REG_ARRAY_SIZE,
>> +};
>> +
>> +struct cpufreq_qcom {
>> +       struct cpufreq_frequency_table *table;
>> +       void __iomem *reg_bases[REG_ARRAY_SIZE];
>> +       cpumask_t related_cpus;
>> +       unsigned int max_cores;
>> +       unsigned long xo_rate;
>> +       unsigned long cpu_hw_rate;
>> +};
>> +
>> +static const u16 cpufreq_qcom_std_offsets[REG_ARRAY_SIZE] = {
> 
> Is this going to change in the future?
> 

Yes, they could change and that was the reason to introduce the offsets. 
This was discussed earlier too with Sudeep and was to add them.

>> +       [REG_ENABLE]            = 0x0,
>> +       [REG_LUT_TABLE]         = 0x110,
>> +       [REG_PERF_STATE]        = 0x920,
>> +};
>> +
>> +static struct cpufreq_qcom *qcom_freq_domain_map[NR_CPUS];
>> +
>> +static int
>> +qcom_cpufreq_hw_target_index(struct cpufreq_policy *policy,
>> +                            unsigned int index)
>> +{
>> +       struct cpufreq_qcom *c = policy->driver_data;
>> +
>> +       writel_relaxed(index, c->reg_bases[REG_PERF_STATE]);
> 
> Why can't we avoid the indirection here and store the perf_state pointer
> in probe? Then we don't have to indirect through a table to perform the
> register write.
> 

As the offsets could change and that was the reason to add this.

>> +
>> +       return 0;
>> +}
>> +
> [..]
>> +static int qcom_resources_init(struct platform_device *pdev)
>> +{
>> +       struct device_node *cpu_np;
>> +       struct of_phandle_args args;
>> +       struct clk *clk;
>> +       unsigned int cpu;
>> +       unsigned long xo_rate, cpu_hw_rate;
>> +       int ret;
>> +
>> +       clk = clk_get(&pdev->dev, "xo");
>> +       if (IS_ERR(clk))
>> +               return PTR_ERR(clk);
>> +
>> +       xo_rate = clk_get_rate(clk);
>> +
>> +       clk_put(clk);
>> +
>> +       clk = clk_get(&pdev->dev, "cpu_clk");
> 
> Sad that the name is cpu_clk, instead of something like 'backup' or
> whatever the name really is in hardware.
> 

Sure, would update it.

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